1. Field of the Invention
The present invention relates to a laminated inductor.
2. Description of the Related Art
A method of manufacturing a laminated inductor has been traditionally known, which comprises printing internal conductor patterns on ceramic green sheets containing ferrite, etc., and then stacking the sheets on top of one another and sintering the stacked sheets.
According to Patent Literature 1, through holes are formed at specified positions in a ceramic green sheet made with ferrite powder. Next, on one main side of the sheet in which through holes have been formed, a coil conductor pattern (internal conductor pattern) is printed using a conductive paste in such a way that when a multiple number of the sheets are stacked and their through holes connected, a helical coil will be formed.
Next, the above sheets having through holes and coil conductor pattern formed in/on them are stacked on top of one another according to a specified structure, after which a ceramic green sheet (dummy sheet) having no through holes or coil conductor pattern is stacked on top and bottom. Next, the obtained laminate is pressure-bonded and sintered, and then external electrodes are formed on the end faces where the ends of the coil are led out, to obtain a laminated inductor. Here, a high L value can be achieved by producing the dummy sheet using a material with high magnetic permeability.
There has been a demand of electrical current amplification for laminated inductors (i.e., offering higher rated currents) in recent years, and to meet this demand, changing the type of magnetic material from ferrite as traditionally used, to soft magnetic alloy, is being considered. Proposed soft magnetic alloys such as Fe—Cr—Si alloy and Fe—Al—Si alloy have a higher saturated magnetic flux density compared to conventional ferrite. On the other hand, these materials have a substantially lower volume resistivity compared to conventional ferrite.